Process of weighting fibers and the product thereof



Patented F b. s, 1935 UNITED STATES .ATENT OFFIC PROCESS OF WEIGHTIN G FIBERS THE PRODUCT THEREOF tors of said Olav Ber No Drawing.

, deceased Original application August 24, 1926, Serial No. 131,310.

Divided and this application March 5, 1929, Serial No. 344,582

15 Claims.

This invention relates to the chemical treatment of fibers, especially those of silk, for the purpose of increasing their size and weight, and to the product of such treatment. Our process tin weighting treatment, which have many advantages both as to the method employed and as to the resultant article, over such as have been known heretofore.

It is customary in the art to treat silk fibers with a solution of tin tetrachloride and to follow this treatment with one in sodium phosphate. These treatments are usually repeated until the desired weight is obtained. But these treatments are expensive and no great amount of such loading is possible without injuring the elasticity and strength of the fibers, making them tender and brittle and subject to deterioration with age.

The important feature of our invention is that apply a treatment with zinc compounds in a neutral or slightly acid solution. The preliminary treatment may be any one of the known methods of tin weighting. We have found that practically any soluble zinc compound can be used, but not all with the same advantage. The result is greatly dependent upon the nature of the solution.

If silk fiber has been preliminarily treated with tin tetrachloride andsodium phosphate, a treatment in zinc sulphate or nitrate will not add materially to the weight and volume of the fiber. This is probably due to the fact that when a small amount of zinc oxide has been taken up by the fiber, sulphuric or nitric acid will have been liberated and will prevent any more oxide from being taken up. We therefore prefer to use a zinc salt of a weak acid, for instance, zinc acetate or formate.

A zinc salt of a strong acid, for instance, zinc sulphate, can be used with the same advantage as a zinc salt of a weak acid, for instance, zinc acetate, if it is used in a buffer solution, that is, in a solution of such a nature that a small addition of acid or alkali will only make a small relative change in the hydrogen-ion concentration. A solution of sodium acetate is suitable for this purpose.

For certain purposes it is of great advantage to use the zinc in an alkaline solution. Such a solution can be prepared by dissolving zinc oxide in a solution of caustic alkali. It may also be prepared by mixing a solution of a zinc salt with ammonia, ammonia being used in suflicient excess to produce a clear solution. Sometimes we prefer to use the zinc salts in an alkaline solution which contains salts of other metals or positive groups. We sometimes use ammonium salts for this purpose.

The process may terminate after the treatment in the solution of the zinccompound, but usually we prefer to follow that step with a treatment in a fixing bath. For this purpose we can use a large variety of different chemicals, such for example, as soluble silicates. We can also use a number of combinations of these and other substances. For instance, as a fixing treatment we can use a bath of sodium phosphate, follow that with a bath of sodium silicate and finally give a treatment in a fatty soap.

The application of a fixing bath has the advantage of increasing the weight and volume of the fiber, and to make the zinc compounds present on the fiber, more insoluble. It also improves the lustre and scroop of the fiber. The fixing bath usually imparts to the fiber the property of taking up more zinc oxide if it is again submerged in a solution of a zinc compound. By thus alternately applying to the fiber a zinc compound and a fixing bath, any desired increase in weight can be obtained.

By the methods now in vogue and employed in the past for the weighting of silk, sodium silicate or other soluble silicates are frequently applied in connection with tin compounds. Silk fibers can be weighted by alternately treating the fiber in a solution of tin tetrachloride and a somary first to subject the fiber to the alternate action of baths of tin tetrachloride and of sodium phosphate and thereafter to treat it in a solu tion of sodium silicate. After silk, for example, has been weighted by alternate treatments in tin tetrachloride and sodium phosphate, it will take up a certain amount of silicate when immersed in a solution of sodium silicate, but after one silicate treatment it has practically no ability to take up more. Such application of sodium silicate will greatly increase the size of the fiber. But silk weighted by tin compounds in connection with sodium silicate is very often tender and brittle and will deteriorate in a comparatively short time.

It is known also that if thefibers after the-silicate treatment are subjected to certain baths of metallic salts, they will take up a further amount of silicate, if they are again subjected -of weighting on the fibers weighting on the to the action of a solution of a silicate. Alternate treatments with metallic salts and a soluble silicate may be repeated again and again until the desired increase in weight and volume is obtained. Each repetition will add to the weight and volume of the fiber.

We have found certain solutions of salt of zinc particularly well suited for application in connection with silicates. For some purposes we prefer to use this metal as a neutral salt, forinstance as an acetate. For other purposes we prefer to use it in alkaline solutions. By our process the treatment in solutions of zinc compounds is applied after a preliminary weighting with tin by any of the known methods. If this foundation of tin weighting contains silicate, the

zinc salts from the solutions we use seem to combine with this silicate to a greater extent than with former processes, and this has the effect of largely minimizing, if not entirely overcoming the detrimental influence of the silicate upon the fiber. Moreover, greater amounts of the metal and the silicate are adsorbed by the fiber at each repetition of these baths.

When tin weighted silk' is treated in a bath of a zinc salt, this bath will have a tendency to turn acid by use. According to our invention we avoid or minimize the effect of this acidity. We have found that when an ordinary zinc salt, such as a zinc sulphate, is used alone, the solution becomes acid to such a degree that it interferes with the absorption of thezinc. Better results are obtained if the zinc bath is maintained in a slightly acid condition, such as between the pH values of a 4.5 and 6.5. We accomplish this by using the zinc salt as a buffered solution. This can be done by using a zinc salt of a weak acid,

such as zinc acetate, (because such a salt will be a buifer in itself between the pH values mentioned) or a zinc salt which is not in itself a buffer can be used, such as zinc sulphate, if to it is added some suitable buffer compound, such for example as sodium acetate. The undesirable increase in acidity, may also be avoided by the addition of 'a suitable alkali, such as sodium borate.

A certain amount of weighting is added to silk fibers according to former methods, by four successive passes through baths of tin tetrachloride and sodium phosphate followed by a treatment in a bath of sodium silicate. According to our invention we find we can get an equal amount by using but three successive passes through baths of tin tetrachloride and sodium phosphate followed by a treatment in such a solution of a zinc salt as above described, followed by another treatment in a bath of sodium silicate.

We also find that by using two successive passes in tin tetrachloride and sodium phosphate, followed by a treatment in the foregoing solutions of a zinc salt and then in a solution of sodium silicate, we obtain the same amount of fibers as is obtained by the former method when three successive passes through tin tetrachloride and sodium phosphate are followed by a treatment in a bath of sodium v silicate.

Thus the desired increase may be obtained without the undesirable use of an excess of tin compounds. By this process the size of the fiber will greatly increase, which is the principal object of any weighting process. The goods are soft and fluffy and their appearance greatly improved. Goods containing a considerable amount of tin weighting with silicate applied by former methods are subject to shrinkage which undesirable characteristic is greatly reduced by this new method. Furthermore, dur treatment is less expensive than 'the former method of repeating tin and phosphate treatments to obtain similar weights.

We have found that the goods may be given a still greater volume with few treatments, if the zinc compound used be in the form of an alkaline solution. For example: By two passes in tin tetrachloride and sodium phosphate, as previously described, the weight of '75 pounds degummed silk will be increased to 102 pounds. A treatment in sodium silicate 3 Baum, F. for one half hour.will bring the weight up to 116 pounds. These steps are old.

We now put the silk in an alkaline bath of a zinc salt, prepared as follows: ammonia is added to a bath of zinc acetate thereby forming a precipitate, but the addition of ammonia is continued until the precipitate is dissolved. This alkaline bath of zinc salt is used at 3 Baum and 140 F. for one hour, after which the goods are washed. This adds somewhat to the weight. When the silicate treatment before described follows, the weight will increase to pounds. Another treatment in the alkaline bath of zinc brings the weight up to pounds. Another bath of sodium silicate gives further increase of weight and volume. Thus the desired weight and volume can be obtained with fewer steps than if zinc had been used in an acid solution. The process may be ended after any of the fixing baths described.

Wefind it desirable to use one or more intercalated treatments with a soluble lead salt, such as lead acetate as described in Patent No. 1,579,628, issued April 6, 1926, as this has the effect of improving the fiber in many ways. It not only increases the weight but improves the tone of the fiber, increases its elasticity, improves its dyeing properties and has a preservative effect. This lead treatment may be applied at any stage after the tin treatment has been applied. We now prefer to follow the lead treatment with a bath of sodium phosphate.

As a specific example, the weight of '75 pounds of boiled off or degummed silk is increased to 102 pounds by two tin tetrachloride and phosphate treatments as before described. After a thorough wash the silk is submerged in a lead acetate solution 3 Baum for one hour at 140 F. washed, and then treated in a slightly alkaline solution of sodium phosphate 6 Baum at 140 F. for; one hour. The weight is then 129 pounds. The silk is then submerged for one half hour in a solution of sodium silicate of 3 Baum at 140 F. The weight is then 142 pounds. The steps so far are old. When the silk is then subjected to a 4 Baum bath of zinc acetate at 140 F. for one half an hour and washed, the weight will not be materially increased. This is probably due to the fact that some sodium will be dissolved oif from the fiber and go into the zinc acetate solution and thereby partly offset the weight of the zinc oxide which at the same time is taken up by the fiber. But this treatment improves the fiber and so changes the characteristics of the material already on it as to make the treated goods capable of taking up more silicate. If after the zinc acetate treatment the silicate treatment previously described, is repeated, the weight is increased to 183 pounds. Another zinc acetate bath followed by another of sodium silitwo sodium of an inorganic cate, again followed by a zinc acetate, finally followed by a treatment with sodium phosphate, will increase the weight to 233 pounds.

The aforesaid lead treatment may be used also in connection with the alkaline process described. In neither case do the lead and zinc compounds interfere with one another, nor does the lead efiect the absorption of zinc or silicate from subsequent baths.

The order and number of steps taken may be varied after the tin treatment has first been applied. The process may be applied to fibers in the skein or to textiles and they may be brought to any desired weight or volume. The treated fibers form a new and useful material.

This description is for illustrative purposes only, as the strengths, temperatures, acidities and times mentioned, as well as the order and number of steps, and even the chemicals specified, may be varied without departing from the scope of the invention and we intend no limitations other than those imposed by the appended claims.

It is understood from this disclosure that the water washing steps, or cleaning with weak acid or alkaline solutions, which are not included in the claims, may be used after each bath specified.

Salts of cadmium may in some cases be substituted for salts of zinc for the purposes of this invention and our invention broadly includesthe use of cadmium compounds as well as of zinc compounds wherever this substitution may be made.

This application is a division of application Serial No. 131,310, filed August 24, 1926.

What we claim is:

l. A process of treating tin weighted fibers which comprises treating such fibers with a zinc salt in a bufler solution and then in a solution of sodium silicate.

2. A process of treating tin weighted fibers which comprises treating such fibers with a solution of an inorganic zinc salt in a buffer solution and then in a solution of sodium silicate.

3. A process of treating tin weighted fibers which comprises treating such fibers with a zinc salt in a solution of low acidity which is maintained at a substantially constant pH value, and then in a solution of sodium silicate.

4. A process of treating tin weighted fibers which comprises treating such fibers in solutions of zinc acetate and of sodium silicate.

5. A process of treating tin weighted fibers which comprises treatingsuch fibers in a solution of sodium silicate, then with a solution zinc salt in a buffer solution, and again in a solution of sodium silicate.

6. A process of treating tin weighted fibers which comprises treating such fibers in a solution of sodium silicate, then with a zinc salt in a solution of low acidity which is maintained at a substantially constant pH value, and again in a solution of sodium silicate.

7. A process of treating tin weighted fibers which comprises treating such fibers in a solution of sodium silicate and then in successive solutions of zinc acetate, of sodium phosphate, and of sodium silicate.

8. A process of treating tin weighted fibers which comprises treating such fibers with a zinc salt in a buffer solution and then in a bath of sodium silicate with an intercalated treatment with a soluble lead compound.

9. A process of treating tin weighted fibers which comprises treating such fibers in a solution of zinc acetate, then in a solution of sodium silicate, and then in a bath of lead acetate.

10. A process of treating tin weighted fibers which comprises treating such fibers in a solution of sodium silicate, then in a solution of zinc acetate, then in a solution of sodium silicate, and then in a bath of lead acetate. 1

11. A process of treating tin weighted fibers which comprises treating such fibers in a solution of sodium silicate, and then in solutions of zinc acetate, of sodium silicate, of lead acetate, and of sodium phosphate.

12. A process of treating tin weighted fibers which comprises treating such fibers in a solution of sodium silicate, and then in successive solutions of zinc. acetate, of sodium silicate, with an intercalated treatment with a soluble lead compound and then in a bath of sodium phosphate.

13. A process of treating tin weighted fibers which comprises treating such fibers with a zinc salt in a solution of low acidity which is maintained at a substantially constant pH value,

and then in a solution of sodium silicate, with an intercalated treatment with a soluble'lead compound.

14. A process of treating tin weighted fibers which comprises treating such fibers with a zinc salt in a solution of low acidity which is maintained at a substantially constant pH value, and then in a solution of sodium silicate, and then with a soluble lead compound.

15. A process of treating tin weighted fibers which comprises treating such fibers in a solution of sodium silicate, then with a zinc salt in a solution of low acidity which is maintained at a substantially constant pH value, and again in a solution of sodium silicate, with an intercalated treatment with a soluble lead compound.

OLAV BERG. MAX IMHOFF. OERNUIF E. HEIBERG. 

